Indicating plug fuse



y 2, 19 0. w. c. LINTQN ,206,786

INDIGATING PLUG FUSE Filed March 6, 1939 Patented July 2, 1940 UNITEDSTATES PATENT orrics LNDICATING PLUG FUSE Application March 6, 1939,Serial No. 289,161

5 Claims. i (Cl. 200-121) The present invention relates to plug typefuses for electrical circuits capable. upon the rupture of the fuse linkor elements thereof, of giving or emitting a visible signal orindication 5 and an object of the invention is to provide a cap or coverfor housing such indicators which may be easily and economically appliedto the casings of many of the conventional plug type fuses for reducingthe cost associated with the manufacture and assembly thereof and whenapplied, will readily designate the amperage ratings of the fuse and yetpermit the signal to be rendered visible when the fuse link or elementsblow or become ruptured due to a short circuit within the electricalcircuit.

Other objects of the invention will be in part obvious and in partpointed out hereinafter.

In order that the invention and its mode of operation may be readilyunderstood by persons skilled in the art, I have in the accompanyingdrawing and in the detailed following description based thereupon, setout an embodiment of the same.

In the drawing:

Fig. L' is a top plan view of the fuse embodying the present invention.

Fig. 2 is a top plan view of the fuse casing.

Fig. 3 is a vertical transverse section taken on the line 3--3 of Fig. lin the direction of the arrow points.

Fig. 4 is a vertical transverse section of the fuse taken at rightangles to that shown in Fig. 3.

Fig. 5 is a plan View of-the separator disc.

Fig. 6 is a bottom plan view of the cap or cover for the fuse.

Fig. 7 is a vertical transverse section through the cap taken on theline 1-4 of Fig. 6 in the direction of the arrow points.

Fig. 8 is another vertical transverse section of the cap or cover takenon the line 8-8 of Fig. 6 in the direction of the arrow points.

Fig. 9 is an enlarged detail section illustrating a connection betweenthe cap or cover and the fuse casing.

Fig. 10 is another detail section.

.Fig. 11 is a detail section illustrating a slightly modified form of aconnection that may be employed between the cover and the fuse casing,and

Fig. 12 is a detail section taken on the line l2--i2 of Fig. 11 in thedirection of the arrow points.

Referring now more particularly to the drawings wherein like andcorresponding parts are designated by similar reference charactersthroughout the several views, there is herein shown a cup-shaped 'casingI molded from porcelain or other insulating material having an explosivechamber 2 formed therein with its upper end open and its lower endcommunicating with an opening I. A vent opening 4 is formed within thecasing having communication with this explosive chamber 2 and the outerside or face of the casing. Molded with the outer surface of the casingare screw threads 5 and an annular flange 6. The lower edge of thisannular flange 6 has the equally spaced recesses 1 formed therein.

Seated within the opening 3 is a rivet 8 forming the central contactterminal of the fuse and engaging the threads 5 is a threaded contactshell 9. A fuse link I has one end soldered to the rivet 8 and itsopposite end extending through the vent opening 4 where its extremity isretained in electrical contact with the shell 9.

A conventional plug type fuse for lighting systems of other electricalcircuits, as above described, usually employs a mica disc for coveringthe upper opened end of the casing I, providing a window, whereby, uponclose examination, one may look through such mica disc to determine thecondition of the fuse link I0 housed within the fuse casing I. In orderto more readily and positively determine the condition of this fuse linkI0, I employ a miniature neon glow lamp which is connected in serieswith the terminals 8 and 9 but in parallel with the fuse link l0 so thatin normal operation, the current will flow through the fusible link H),but should this link l0 become blown or ruptured, the current will passthrough the lamp ll, causing the latter to emit a visible signal forannouncing the inoperative condition of the fuse link.

This lamp rests horizontally upon the upper outer face of the casing land has a lead wire l2 connected to the contact shell 9 by means of aleak resistance l3. This leak resistance l3 preferably consists of aplastic composition inserted within a cavity l4 formed within the casingl. The other lead wire l of the lamp is seated within a groove l6 formedin the casing I and has its outer extremity electrically connected tothe rivet 8. This wire conductor I5 is covered by means of plasticcement il in order that the same may be retained within the groove l6and further be protected from the molten metal that is sometimes givenoff by the blowing of the fuse link I, which would likely damage thewire 15 and thereby interfere with the successful operation of the lamp.Also, a small amount of plastic 'cement may be inserted within the ventopening 4 as at i8 for sealing the same against dust, lint and the likeentering the explosive chamber 2 of the fuse casing, which would'likelycause damage to the fuse when the fusible link blows.

The upper end of the casing I is provided with an annular groove la inwhich is loosely seated a disc I8 01 flber or other suitable materialhaving flreresisting qualities and which disc acts as a separator aswell as a protector for the lamp ii against the molten metal or hotgases given oif by the blowing of the fuse link iii, which would likelydiscolor the glass tube of the lamp or in any other manner interferewith the operation thereof.

In order to seal the upper opened end of the casing I and properlyretain the lamp ii thereupon, I provide a cap or cover 20 which consistsof a transparent or translucent material whereby the light rays from thelamp may be proiected therefrom and rendered visible from the exteriorof the cover.

This cover is preferably molded from thermosetting molding materialssuch as Bakelite but could be molded from other transparent mate-- rialssuch as glass and Pyrex or from thermoplastic molding materials such ascasein, cellulose acetate derivatives, polymerized derivatives ofmethacrylic acid and the like.

This cover comprises a disc-shaped body portion 2| having depending fromits outer edges an annular flange 22 and a bulged portion 23 extendingdiametrically across the body portion 2|, which latter provides acompartment 24 in which is housed the lamp The lower face of the discportion 2| of the cover rests upon the upper outer face of the annularflange 6 of the casing and the flange portion 23 of the cover extendsabout the outer side wall of the flange 6 and may be connected theretoby'means of a plastic cement 25. This plastic cement 25 is insertedbetween the flange 23 and the outer face of the flange 6 of the casing iat several points, whereby,

a portion of the plastic material will also be seated within therecesses 1 formed in the underside of the flange 6, thereby preventingthe rotation or removal of the cover 20 from the casing I. This plasticmaterial being applied only at spaced intervals between the recesses 7permits the gases under pressure to escape from the explosive chamber 2between the cover and the casing at such points where the plastic cementis not applied.

The outer face of the bulged portion 23 of the cover may have molded orotherwise placed thereupon the volt and amperage ratings of the fuse towhich the cover is applied such as designated by 15 a.--125 v. Also, theouter face of the flange 22 of the cover has formed therewith serrations26 or other suitable projections which would facilitate the turning ofthe fuse into and out of its fuse socket.

This cover 20 is preferably formed from transparent or translucentmaterials in order that the rays of light from the lamp may projecttherethrough and these transparent or translucent materials may beprepared in various colors so that a colored top may be employed fordesignating the particular amperage rating of the fuse and, further, acolored'light will be visible when the fuse link ill blows for not onlysignalling the blown condition of the fuse, but for visibly desigmatingthe amperage rating of the fuse. The

separator disc l8 being opaque, hides from view the interior of thecasing as well as the fuse link ill but the upper face of this disc I!may have a suitable reflecting surface, especially that portion thereofwhich is placed directly below the lamp II.

In the event the vent opening 4 is closed by means of the plastic cementl8 and the fuse link i is blown, the gases under pressure arising fromthe blown fuse will cause the disc I! to be raised from its seat orgroove l8, whereby the gases may escape by the disc and between thecover and the annular flange 8 of the casing to the atmosphere. Thisretarded exit of the gases under pressure or the flame given off by theblowing of the fuse link ill will prevent any inflammable material thatmay be placed about the fuse from becoming ignited.

In addition to fastening the cover upon the fuse casing by means of theplastic cement 25, I employ a snap flt between the cover and the casingto which it is applied by forming with the lower edges of the flange 22of the cover inwardly projecting ribs 21. In the drawing, 1 haveillustrated three inwardly projecting ribs 21 but a single rib may beemployed and which rib or ribs may be forced over the upper bevelledface of the annular flange 8 until they pass below the lower edge of theflange 6 where they will snap by this lower edge and be seated below thelower face of the flange 8, thereby preventing the cover from beingwithdrawn from the casing I. By the application of the plastic cementbetween the flange 22 of the cover and the recesses I of the casing, thecover will be prevented from rotating upon the casing. When the casingis molded from plastic molding materials, it has sufficient resiliencyto permit the flange 22 of the casing to give, in order that the ribs 21may be forced over the outer face of the flange 6 of the casing Theinner face of the disc portion 2| and flange 22 of the cover may haveL-shaped grooves 28 formed therein which act as vents for permitting thegases under pressure arising from the explosive chamber 2 to escape in aretarded manner by the cover into the atmosphere.

In the modification as illustrated in Fig. 11 of the drawing, the outerwall of the annular flange 8 of the casing i has formed therein aplurality of vertically extending grooves or recesses in which areseated correspondingly formed ribs 28 projecting from the inner face ofthe flange 22 of the cover, in order that the cover, when being appliedto the casing, will be prevented from rotating thereupon, due to thegeared connection that is effected by the ribs 29 extending through therecesses formed within the annular flange 6.

The interior diameter of the flange 22 should be slightly less than theexterior diameter of the annular flange 6 in order that a wedgedconnection can be effected between the cover and the casing, therebyeliminating the necessity of plastic cement or similar fasteningelements or composition between the cover and the casing. Beforeapplying the cover to the casing, it may be slightly heated in order torender flange 22 somewhat plastic or more flexible, as would permit itto freely pass over the outer face of the flange 6 and when the cover isallowed to cool, it will be shrunk tightly upon the flange, therebypermitting the withdrawal of the cover from the casing and the gearedconnection consisting of the grooves or ribs 29 will prevent therotation of the cover upon the casing. When employing thermo-settingmolding materials and the like iii) where it is impossible to render thecover again plastic or flexible, I employ a casing I made of porcelainand subject this porcelain casing to a low temperature sufficient toshrink the casing and, particularly, its annular flange 6, whereby thecover may be inserted over such shrunk casing and when the latterreturns to normal atmospheric temperatures, it will expand, therebyeffecting a wedged connection between the flange 22 of the cover and theannular flange 6 of the casing. I reduce the temperature of theporcelain casing I by simply placing dry ice upon the flange 6 of thecasing during the assembling operations of the fuse. The verticalgrooves within the outer face of the annular flange 6 may be ofdifierent depths in order that several of the ribs 29 may not completelyclose several of these grooves, whereby, the gases under pressure fromthe explosive chamber 2 may pass therebetween and escape to theatmosphere or the form of cover shown in Fig. 11 may have ventinggrooves corresponding to the L-shaped grooves [6, as better shown inFigs. 6 and 10 of the drawing, whereby the gases under pressure escapefrom the explosive chamber 2. When not employing such ventilating meansbetween the casing and the cover therefor, the plastic cement I! may beremoved from the vent opening 4 whereby the gases from the explosivechamber 2 may escape through this vent opening 4 in the customarymanner.

Maniiestly, the construction herein shown is capable of considerablemodification and such modifications as come within the scope of myclaims, I consider within the spirit of my invention.

I claim:

1. An indicating fuse comprising a casing having a pair of contactterminals and an explosive chamber formed therein, a fuse link arrangedwithin said chamber and connected to said terminals, a glow lamp andleak resistor connected in series with said terminals but in parallel tosaid fuse link, a transparent cover for housing said lamp, a dependingand flexible flange formed with said cover, projections formed with thelower end of said depending and flexiible flange, an annular flangeformed with said casing and arranged within said depending and flexibleflange of said cover whereby when the flange of said cover is forcedover said annular flange said projections will pass thereover and engagewith the lower face of said annular flange to prevent the removal oisaid cover from said casing and means for preventing the rotation ofsaid cover upon said casing.

2. An indicating ruse comprising a casing having a pair oi contactterminals and an explosive chamber iormed therein, a fuse link arrangedwithin said chamber and connected to said terminals, a glow lamp andleak resistor connected in series with said terminals but in parallel tosaid use link, an annular flange formed with said casing, a cover havinga bulged portion for receiving said lamp, the walls of said bulgedportion of the cover being transparent whereby the rays of light fromsaid lamp may pass therethrough, an annular depending flange formed withsaid cover and extending about said annular flange formed with saidcasing, and means for connecting said depending flange of the cover tothe annular flange of said casing.

3. An indicating fuse comprising a casing having a pair or contactterminals and an explosive chamber formed therein, a fuse link arrangedwithin said chamber and connected to said terminals, a glow lamp andleak resistor connected in series with said terminals but in parallel tosaid fuse link, an annular flange formed with said casing having aplurality of recesses formed therein, a cover for housing said lamp, aplurality of projections formed with said co'iver and arranged withinthe recesses formed within said annular flange and mean-s for connectingsaid cover to said casing.

4. An indicating fuse comprising a casing having a pair of contactterminals and an explosive chamber formed therein, a fuse link arrangedwithin said chamber and connected to said terminals, a glow lamp andleak resistor connected in series with said terminals but in parallel tosaid fuse link, an annular flange formed with said casing having aplurality of vertically extending recesses formed within the outer wallthereof, a partition arranged within said casing, a cover for housingsaid lamp and retaining the latter upon said partition, a flange formedwith said cover, a plurality of projections formed with said flange oithe cover and fitted within the recesses of said annular flange andmeans for preventing the withdrawal of said cover from said casing whenseated thereupon.

5. An indicating fuse comprising a casing having a pair of contactterminals and an explosive chamber formed therein, a fuse link arrangedwithin said explosive chamber and connected in series with saidterminals, a glow lamp and leak resistor connected in series with saidterminals but in parallel to said fuse link, said casing being formedfrom a material having a relatively high temperature coemcient oicontraction, a cover for housing said lamp and leak resistor, a flangeformed with said cover having an interior diameter less than that of thenormal exterior diameter oi said casing whereby when said casing hasbeen contracted, said flange may fit thereover and means forestablishing a wedged connection between said cover and easing.

'WL' UAli E C. LENTQES.

